Increasingly, the internet communication infrastructure is used to provide access to multimedia content such as TV content. This ranges from user-contributed material, to advertising-sponsored material, to premium content. The premium content material is often distributed at high quality and may consist of recently released movies or live events such as popular sports events and concerts.
Premium content is often secured by a Digital Rights Management (DRM) system. DRM technology is well known and there are a number of DRM systems presently available for distributing content to clients. A DRM system typically consists of creating a file with encrypted content, a description of the usage rules, and a content decryption key encrypted with a key associated with a specific DRM client. The DRM protected content can be distributed to the client as a file or as a stream. The DRM client first processes the usage rules, and possibly the encrypted version of the content decryption key, before starting the decryption of the content data. In general, the DRM client is implemented in a secured software application and is often closely integrated with the content player.
Premium content is commonly delivered (or “streamed”) using Internet Protocol TV (IPTV). IPTV is a system through which multimedia services such as television/video/audio/text/graphics/data may be delivered over IP based networks that are managed to provide the required level of quality of service and experience, security, interactivity and reliability. In particular, IPTV provides secure and reliable delivery to subscribers of entertainment video and related services. These services may include, for example, Live TV, Video On Demand (VOD) and Interactive TV (iTV). These services are delivered across an access agnostic, packet switched network that employs the IP protocol to transport the audio, video and control signals. In contrast to video over the public Internet, with IPTV deployments, network security and performance are tightly managed to ensure a superior entertainment experience, resulting in a compelling business environment for content providers, advertisers and customers alike.
Live content is often distributed in a stream since the content file only is complete at the end of the event. Apple's HTTP Live Streaming (HLS), Microsoft's Smooth Streaming, and Adobe's HTTP-based Dynamic Streaming (HDS) are content delivery solutions that use standard HTTP web servers to deliver streaming content, obviating the need for a streaming server. HTTP packets are firewall friendly and can utilize standard HTTP caching servers on the web. This decreases total bandwidth costs associated with delivering the video, since more data can be served from web-based caches rather than the origin server, and it improves quality of service, since cached data is generally closer to the viewer and thus more easily retrievable.
Special “adaptive streaming” protocols exist that enable a subscribing client to adapt to dynamic changes in the effective data rate with which content can be streamed to the client. Typically, such protocols require the server to prepare different data rate encodings of the content. If the client sees a change in data rate, it can switch to a encoding version that matches the changed transmission conditions. In order to reduce the bandwidth, the adaptive streaming protocols are designed to facilitate caching of portions of the content in the nodes of the distribution network. These caches require that a content portion has a unique identifier, so each cache can determine if it can fetch the content portion from local storage or it needs to pass on the content request to a node closer to the server. HTTP-based adaptive streaming technologies generally have two components: the encoded audio-visual content chunks themselves, and the manifest file that identifies the content chunks for the player and contains their URL addresses. The MPEG DASH (ISO/IEC 23009-1) draft standard may eventually replace most of the proprietary adaptive streaming formats.
A common attack against the live streaming of premium content (e.g. sports and concerts) consists of an authorised client grabbing the decoded output (e.g. by simply using a camera), processing it in a content encoder, and redistributing the re-encoded material in an unauthorised manner (e.g. using P2P or another infrastructure). Often the redistribution of the content uses protection technology to enable the attackers to charge a fee for their unauthorised service.
What is needed is a countermeasure against such redistribution attacks that is suitable for disturbing the unauthorised redistribution service. The present invention aims to provide such a countermeasure.